The goals of comScore’s research, of course, is to make the case for panel data in accurately measuring audience. Fred’s conclusion is more general:

You cannot rely on your own analytics data. You need third party data as well. That’s not to say that third party data (primarily panel data) is perfect either. You have to triangulate between all the numbers to get a decent view of what’s actually going on.

Undercounting conversions

All of that said, I titled this post “undervaluing web audiences” because I think there is an interesting flipside to the big “audience is overcounted by 2.5x” message of the study. If audiences are overcounted by this much, and those overcounts apply to ad impressions as well as overall unique visitor counts (according to the study, unique ad impressions were indeed part of the analysis), then there is likely some depression of conversion rates in many of the cookie-based analytics tools.

I’m sure that some simple conversion paths are exempt from this problems: a click on a search ad that results in a conversion during the same browser session is unlikely to suffer from any of the cookie-related issues outlined in the study. More complex paths, however, such as those based on brand impressions, repeated display ad impressions or deferred conversions, are likely to be undercounted by the same measure as the unique audience.

The behavioral ad networks are known for the application of their technology to targeting. Another key asset, however, is the ability to measure the value and ROI of online brand advertising. They use their networks, based largely on cookies, to track the deferred conversions that prove the value of a brand impression campaign.

If they are undercounting these conversions by 2.5x, perhaps current impressions are undervalued such that a correction for overcounting of audience would need to be somewhat offset by an adjustment to effective CPM for the brand ads run on the site. In any case, I’m sure advertisers doing brand impression campaigns, as well as the ad networks, will want to figure out how to more effectively measure deferred conversions if cookies present such significant accuracy problems. It sounds like Tacoda might be using comScore’s data to try to adjust.